libcamera: software_isp: Add CCM algorithm

This patch adds color correction matrix (CCM) algorithm to software ISP.
It is based on the corresponding algorithm in rkisp1.

The primary difference against hardware pipelines is that applying the
CCM is optional.  Applying CCM causes a significant slowdown, time
needed to process a frame raises by 40-90% on tested platforms.  If CCM
is really needed, it can be applied, if not, it's better to stick
without it.  This can be configured by presence or omission of Ccm
algorithm in the tuning file.

CCM is changed only if the determined temperature changes by at least
100 K (an arbitrarily selected value), to avoid recomputing the matrices
and lookup tables all the time.

Since the CCM is float, rather than double, to use the same type as in
the rkisp1 pipeline, the type of color gains is changed from double to
float.

The outputs of the algorithm are not used yet, they will be enabled in
followup patches.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

5 files changed, 121 insertions, 3 deletions

diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
index 4e31e386..ec77c6e5 100644
--- a/src/ipa/simple/algorithms/awb.cpp
+++ b/src/ipa/simple/algorithms/awb.cpp
@@ -59,9 +59,9 @@ void Awb::process(IPAContext &context,
 	 */
 	auto &gains = context.activeState.awb.gains;
 	gains = { {
-		sumR <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumR,
+		sumR <= sumG / 4 ? 4.0f : static_cast<float>(sumG) / sumR,
 		1.0,
-		sumB <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumB,
+		sumB <= sumG / 4 ? 4.0f : static_cast<float>(sumG) / sumB,
 	} };
 
 	RGB<double> rgbGains{ { 1 / gains.r(), 1 / gains.g(), 1 / gains.b() } };
diff --git a/src/ipa/simple/algorithms/ccm.cpp b/src/ipa/simple/algorithms/ccm.cpp
new file mode 100644
index 00000000..86e0395c
--- /dev/null
+++ b/src/ipa/simple/algorithms/ccm.cpp
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Ideas On Board
+ * Copyright (C) 2024-2025, Red Hat Inc.
+ *
+ * Color correction matrix
+ */
+
+#include "ccm.h"
+
+#include <libcamera/base/log.h>
+#include <libcamera/base/utils.h>
+
+#include <libcamera/control_ids.h>
+
+namespace {
+
+constexpr unsigned int kTemperatureThreshold = 100;
+
+}
+
+namespace libcamera {
+
+namespace ipa::soft::algorithms {
+
+LOG_DEFINE_CATEGORY(IPASoftCcm)
+
+int Ccm::init([[maybe_unused]] IPAContext &context, const YamlObject &tuningData)
+{
+	int ret = ccm_.readYaml(tuningData["ccms"], "ct", "ccm");
+	if (ret < 0) {
+		LOG(IPASoftCcm, Error)
+			<< "Failed to parse 'ccm' parameter from tuning file.";
+		return ret;
+	}
+
+	return 0;
+}
+
+void Ccm::prepare(IPAContext &context, const uint32_t frame,
+		  IPAFrameContext &frameContext, [[maybe_unused]] DebayerParams *params)
+{
+	const unsigned int ct = context.activeState.awb.temperatureK;
+
+	/* Change CCM only on bigger temperature changes. */
+	if (frame > 0 &&
+	    utils::abs_diff(ct, lastCt_) < kTemperatureThreshold) {
+		frameContext.ccm.ccm = context.activeState.ccm.ccm;
+		context.activeState.ccm.changed = false;
+		return;
+	}
+
+	lastCt_ = ct;
+	Matrix<float, 3, 3> ccm = ccm_.getInterpolated(ct);
+
+	context.activeState.ccm.ccm = ccm;
+	frameContext.ccm.ccm = ccm;
+	context.activeState.ccm.changed = true;
+}
+
+void Ccm::process([[maybe_unused]] IPAContext &context,
+		  [[maybe_unused]] const uint32_t frame,
+		  IPAFrameContext &frameContext,
+		  [[maybe_unused]] const SwIspStats *stats,
+		  ControlList &metadata)
+{
+	metadata.set(controls::ColourCorrectionMatrix, frameContext.ccm.ccm.data());
+}
+
+REGISTER_IPA_ALGORITHM(Ccm, "Ccm")
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/simple/algorithms/ccm.h b/src/ipa/simple/algorithms/ccm.h
new file mode 100644
index 00000000..f4e2b85b
--- /dev/null
+++ b/src/ipa/simple/algorithms/ccm.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024-2025, Red Hat Inc.
+ *
+ * Color correction matrix
+ */
+
+#pragma once
+
+#include "libcamera/internal/matrix.h"
+
+#include <libipa/interpolator.h>
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::soft::algorithms {
+
+class Ccm : public Algorithm
+{
+public:
+	Ccm() = default;
+	~Ccm() = default;
+
+	int init(IPAContext &context, const YamlObject &tuningData) override;
+	void prepare(IPAContext &context,
+		     const uint32_t frame,
+		     IPAFrameContext &frameContext,
+		     DebayerParams *params) override;
+	void process(IPAContext &context, const uint32_t frame,
+		     IPAFrameContext &frameContext,
+		     const SwIspStats *stats,
+		     ControlList &metadata) override;
+
+private:
+	unsigned int lastCt_;
+	Interpolator<Matrix<float, 3, 3>> ccm_;
+};
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
index 063bec73..3a3daed7 100644
--- a/src/ipa/simple/algorithms/lut.cpp
+++ b/src/ipa/simple/algorithms/lut.cpp
@@ -103,7 +103,7 @@ void Lut::prepare(IPAContext &context,
 		const double div = static_cast<double>(DebayerParams::kRGBLookupSize) /
 				   gammaTableSize;
 		/* Apply gamma after gain! */
-		const RGB<double> lutGains = (gains * i / div).min(gammaTableSize - 1);
+		const RGB<float> lutGains = (gains * i / div).min(gammaTableSize - 1);
 		params->red[i] = gammaTable[static_cast<unsigned int>(lutGains.r())];
 		params->green[i] = gammaTable[static_cast<unsigned int>(lutGains.g())];
 		params->blue[i] = gammaTable[static_cast<unsigned int>(lutGains.b())];
diff --git a/src/ipa/simple/algorithms/meson.build b/src/ipa/simple/algorithms/meson.build
index 37a2eb53..2d0adb05 100644
--- a/src/ipa/simple/algorithms/meson.build
+++ b/src/ipa/simple/algorithms/meson.build
@@ -4,5 +4,6 @@ soft_simple_ipa_algorithms = files([
     'awb.cpp',
     'agc.cpp',
     'blc.cpp',
+    'ccm.cpp',
     'lut.cpp',
 ])